The subject matter herein relates to the subject matter of concurrently filed application Ser. No. 85,151, filed Oct. 15, 1979, entitled "Pressure Regulator System".
This invention relates to solenoid valve assemblies. More particularly, this invention relates to an improved solenoid valve assembly including means for optimizing the capacity of a relatively small solenoid to open a relatively high pressure valve member.
Solenoid valve assemblies in general are well known in the art. These solenoid valve assemblies typically comprise an electric core which is energizable to displace magnetically an armature through a generally linear stroke path of predetermined length. The armature cooperates with a suitable valve member to shift the valve member upon energization of the solenoid from an open to a closed position, or vice versa, as desired.
Solenoid valve assemblies are used in a wide variety of hydraulic and/or pneumatic system applications wherein the valve member opens and closes a path to fluid flow. In these applications, the valve member is subjected to a prescribed system pressure differential when in a closed position, whereby the solenoid valve assembly is designed to provide sufficient opening forces to overcome this pressure differential in order to move the valve member to an open position. Clearly, it is desirable to design the winding and armature of the solenoid valve assembly to have a minimum size to reduce electrical power requirements and attendant heating of the unit. However, it is well known that the force output of a solenoid armature is relatively small upon initiation of stroke movement, and increases with stroke length. In contrast, opening movement of the valve member requires maximum force application during initial lifting of the valve member from a valve seat, and decreases with further movement of the valve member away from the valve seat.
In the prior art, many solenoid valve assemblies are designed to provide an opening force during initial armature stroke which is sufficient to lift the valve member from a valve seat. This results in a relatively oversized winding and armature with excessive power consumption and heating. These problems are particularly pronounced when the solenoid valve assembly is used in relatively high pressure fluid systems, such as pressure activated starting systems for gas turbine machines, pneumatic gun drives, and the like, wherein the pressure differential across the valve member is on the order of several thousand p.s.i.
Some prior art systems have attempted to overcome the inherent force-stroke mismatch between the solenoid valve assembly and the associated valve member by using a so-called impact solenoid. The impact solenoid comprises a movable armature which cooperates with the valve member through limited lost motion apparatus. With these devices, the armature does not engage the valve member for opening movement until the latter, higher force stages of armature stroke to allow use of relatively smaller solenoid components to open the valve member. See, for example, U.S. Pat. Nos. 2,612,188; 2,735,644; 3,043,336; 3,450,353; 3,473,780 and 3,974,998. However, these impact solenoid designs still have not maximized the capacity of a relatively small and inexpensive solenoid valve assembly to operate a valve member.
The present invention overcomes the problems and disadvantages of the prior art by providing an improved solenoid valve assembly including means for maximizing the capacity of the solenoid to move a valve member to an open position.